Senior examiners have attacked the “perverse incentives” of school league
tables as GCSE grades plummeted by a record level.

The heads of Britain’s biggest exam boards warned that a decline in pass marks was directly linked to the escalating trend of entering pupils for early GCSEs.

Rising numbers of children are taking exams at the age of 15 – rather than the usual 16 – to “bank” a good grade before moving onto other subjects.

It also gives pupils more time to resit if they fail to gain A* to C grade passes at the first attempt – boosting schools’ positions in official rankings. At least two pupils took maths GCSE exams eight times in just 12 months.

But examiners insisted that children were significantly less likely to gain good marks – or properly understand subjects – if they sit GCSEs at 15 rather than 16.

Andrew Hall, the chief executive of AQA, Britain’s biggest exam board, warned that the practice was doing “real damage” to pupils’ education, particularly in key subjects such as maths.

It came as figures showed the number of pupils gaining good marks dropped for the second time in two years today – reversing more than two decades of rising grades in the run up to 2012.

In all, the proportion of test papers awarded at least a C – considered a good pass – was down by 1.3 percentage points to 68.1 per cent.

Data released by the Joint Council for Qualifications showed that the overall proportion of tests marked A* or A fell by more than one percentage point to 21.3 per cent.

Elite A* grades alone fell by 0.5 percentage points to 6.8 per cent and the overall pass mark fell for the first time in six years.

It represents a record drop in top-end GCSE grades following marginal declines at A* to C last summer.

The move was partly down to a huge shift towards “tougher” GCSE subjects this year and a decline in the number of pupils taking less rigorous courses.

But examiners claimed that more pupils were also taking GCSEs early or resitting exams multiple times in a move that it is likely to contribute to significant falls in performance levels.

According to figures, the number of 15-year-olds taking at least one GCSE soared by more than a third – from 416,477 to 507,568.

State schools in England are currently ranked by the number of pupils gaining five A* to C grades, including English and maths, and examiners fear the pressure to climb league tables is driving the trend in “early and often” GCSEs.

Mr Hall said: “I have a real worry that students are getting entered at 15. If they get their C, do they carry on and actually develop to their full potential?

“Or is the accountability system actually saying, ‘well, we'll get them to the C and then they stop’. I think that is the perverse incentive [of the system].”

Mark Dawe, chief executive of the OCR exam board, said: “Early entry does not benefit the students. The results are far lower for 15-year-olds - these qualifications are designed for 16-year-olds.

"Students should be left to learn for those two years and that is what we would encourage."

Most pupils are opting to take maths early or resit the exam multiple times in an attempt to boost their grade.

Separate figures show one-in-10 pupils – 89,353 – sat maths GCSE at least three times this year. Some 38 pupils took it seven times and two teenagers actually took it on eight occasions in just 12 months.

Mr Hall said: "Mathematics, for me, is the biggest concern out of all of this, that repeated and multiple entry - I think it's doing real damage to education in this country."

Katja Hall, chief policy director for the Confederation of British Industry, said:

“The sheer scale of multiple and early entries is astonishing. Employers don’t want exam robots – they want young people who are academically stretched, rounded and grounded.

“Turning schools into exam factories and cramming two years’ syllabus into one benefits no one.”

Stephen Twigg, the Shadow Education Secretary, said: “There has been a big increase in the number of young people taking two or more exams in the same subject. This is bad for standards, school budgets and learning.”

The Government insists it is overhauling league tables to reduce the incentive to bank C grades and cutting down on exam resits.

A Department for Education spokesman said: "The abuse of early and multiple entries is one of the reasons why this Government's reforms of GCSEs are so badly needed.

"Schools should not be entering children for exams early, and then for re-sits, or other exams in the same subject. It is not good for pupils and should not happen.

“It is clearly a worry that some schools might be putting pupils for early entry so they can ‘bank’ a C rather than studying the subject for another year and perhaps getting a better grade.

"Scrapping modules and moving to end-of-course exams will help stop schools 'gaming' the system in this way.

“We also plan to change the way the performance tables are calculated to give schools more credit for each extra grade a pupil achieves. This will encourage schools to enter pupils for GCSEs at the end of Year 11 when pupils are most likely to gain their best grade.

"The fact that Ofsted now challenge the use of inappropriate early and multiple entry to GCSE exams during inspections means schools are in danger of being found out if they do this."